The present invention relates to kilns. More particularly the present invention relates to arrangements for preventing heat leakage from kilns.
It is known in the art to provide a kiln with a plurality of rotatable rollers serving to transport the items to be heat treated in the kiln. Usually, the rollers are all driven rollers. In order to be driven, each roller has a portion extending outwardly through the side walls of the kiln to be with a driving means located outside the kiln. For this purpose, the side wall is provided with a longitudinally extending row of bricks, each brick housing at least one throughgoing hole for receiving its respective roller.
The diameter of each hole must be larger than that of the roller located therein in order to permit the roller to rotate in the hole in spite of distortion of the hole caused by thermal expansion. However, the gap between the outer surface of the roller and the inner surface of the hole tends to permit undesirable leakage of heat from the interior of the kiln. The cumulative amount of heat leaking through all such clearances becomes a serious problem, since the number of rollers is larger.